SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

Soil and Groundwater Investigation Report Vernalis Pump Station August 2006 drinking water Maximum Contaminant Levels and generally prohibits adverse effects on beneficial uses), Toxicity(which prohibits toxic chemicals in toxic amounts), and Tastes and Odors (which prohibits adverse tastes and odors or nuisance conditions). Where more than one WQO is specified for any single chemical constituent,the lowest,most conservative concentration was used for contaminant delineation purposes. In Tables 4 and 5,the groundwater sample analytical results are summarized and compared to the WQOs to assess whether any further characterization is appropriate. A map presenting the concentrations of dissolved constituents of concern in groundwater is provided on Figure 4. Copies of the groundwater sample laboratory analytical reports are included in Appendix C. Laboratory analytical testing detected constituents of concern in the following groundwater samples: • TPHd,benzene, and toluene in SB-22; • TPHd in SB-23; • PAHs(fluoranthene,naphthalene,phenanthrene),TPHd, and TPHd with a silica-gel cleanup (TPHdsg)in SB-25; and • PAHs(acenaphthene, fluoranthene, fluorene,naphthalene, and phenanthrene)in SB-36. Of the detected constituents of concern,the following exceeded WQO action levels: • TPHd and benzene in SB-22; • TPHd in SB-23; and • TPHd and TPHdsg in SB-25. The benzene level of 0.5 gg/L in SB-22 is above the WQO of 0.15 gg/L for toxicity,which is the California Public Health Goal established by the California Office of Environmental Health Hazard Assessment. (The benzene level is less than the enforceable California Primary Maximum Contaminant Level of 1.0 gg/L.) Several PAHs were detected in grab groundwater sample SB-25;however, all results were well below the corresponding WQOs. Aside from benzene in SB-22,no other BTEX compound was detected in any of the groundwater samples. TPHg were not detected in any of the five grab groundwater samples. Laboratory analytical results showed TPHd concentrations of 780 gg/L in SB-22, 560 gg/L in SB-23, and 660 µg/L in SB-25,levels that are all greater than the WQO of 100 µg/L. However, laboratory testing with silica-gel preparation reduced the TPHd levels in the SB-22 and SB-23 samples to non-detectable levels. Only the TPHd(with silica-gel preparation)in SB-25, at a concentration of 240 gg/L,remained above the WQO. Silica-gel preparation reduced TPHd levels by at least 64 percent. Thus, detections of TPHd are mostly polar organic matter,resulting from the intrinsic biodegradation of residual petroleum. Based on the levels of TPHd detected in groundwater samples collected from past Geomatrix soil borings ASB-1,ASB-4,ASB-5,ASB-6,ASB-7, and ASB-11,and the TPHd and benzene found in SB-22, a plume of affected groundwater exists on the Arcos property. Since there have been no borings advanced down gradient of this area and off site,the down-gradient extent of affected groundwater is not delineated. On the off-site Bogetti property, TPHd concentrations in boring SB-25 and in nearby monitoring well MW-7 exceed the WQO. Thus,the extent of affected groundwater is undefined off site and down gradient on the Bogetti property. The affected groundwater on the Bogetti property appears to originate on the easternmost part of the Bellini property in the vicinity of Geomatrix soil borings SB-15 and SB-16. 6 From Science to Solutions-